Variable load burner construction



Dec. 31, 1957 T. s. -VOORHE|S VARIABLE LOAD BURNER CONSTRUCTION Filed.June 22, 1953 2 Sheets-Sheet l INVENTOR. TEMPLE 5. VOORHE/S 4 TTOR/VEY8 Dec. 31, 1957 T. s. VOORHEIS 2,8

VARIABLE LOAD BURNER CONSTRUCTION Filed June 22, 1953 2 Sheets-Sheet 2INVENTORN TEMPLE 8. VOORHE/S VARIABLE LOAD BURNER CONSTRUCTION Temple S.Voorheis, San Francisco, Calif.

Application June 22, 1953, Serial No. 363,211

2 Claims. (Cl. 1581.5)

This invention relates to a new and improved variable load burnerconstructions.

In commercial forced air draft oil and gas burners used to generate heatfor boilers or the like, it is frequently desirable that such burners becapable of 6113- ciently operating over a relatively broad firing rangeto meet greatly varied load conditions.

More particularly, in many industrial heating applications in connectionwith which burners are used, maximum efficiency in over-all operation isattainable only if the burner is capable of successfully operating withsubstantially equal efiiciency at both a relatively high and relativelylow firing rate. Thus, for example, it has been found that in manyinstances, the burner should be capable of operating substantiallyequally satisfactorily anywhere within a ten-to-one load range, or, inother words, that the burner should be capable of operating efiicientlyat as low as one-tenth of its maximum capacity or firing rate.

Although several of the more conventional forced air draft oil or gasburners in commercial use today of which I have knowledge are capable ofoperating reasonably efficiently and satisfactorily over a one-to-fouror one-tofive firing range, if one attempts to operate such conventionalburners at much below one-fourth or one-fifth of their maximum firingrate serious practical difliculties to the point of actual failure incombustion may result.

Perhaps the principal reason why prior art burners cannot be operatedsuccessfully at much below one-fourth or one-fifth of their maximumcapacity is that no sufficiently satisfactory means has heretofore beendeveloped for insuring an adequate or proper intermixture between airand fuel within the combustion chamber under conditions where both thevolume of air and fuel introduced into the combustion chamber is lessthan one-fourth or one-fifth of the amounts introduced into the chamberwhen the burner is operated at maximum capacity.

It is a principal object of the present invention, therefore, to providea burner construction which is capable of operating satisfactorily andefiiciently over a relatively broad firing range, as, for example, overa ten-to-one firing range.

In the drawings:

Fig. l is a side elevational view of a burner construction embodying theinvention with portions thereof shown broken away in section.

Fig. 2 is a plan view of the burner with the fan motor cover removed.

Fig. 3 is an enlarged longitudinal sectional view of the burner proper.

Fig. 4 is an enlarged perspective view of one of the air register vanes.

Fig. 5 is an enlarged fragmentary view in side elevation showing the airregister vanes, in closed position.

Referring now more particularly to the drawings, the burner constructiontherein shown comprises, generally a blower or fan assembly A, a plenumor windbox unit B, an air register assembly C,a gas burner assembly D,an

" ice oil injection assembly E, and a combustion chamber, the entranceto which is designated generally at F.

'lhe tan or blower assembly, neretorote indicated generally at A,preferably comprises a motor-drlven tan blower 10 mounted for rotationwlthln a scroll type or volute tan housing 11. 'lhe motor 12 connectedby belt drive 1.5 to drive shaft 14 may be convemently located withinenclosed Cover 1: removably secured to tan housing 11. the blowerdischarge end or the tan nOLlSlDg is connected as at 10 to the inletside or the plenum or windbox heretolore indicated generally at B.

As above indicated, windbox 5 consists of a scroll type or volute casing11 which may be provided with one or more internal names such asindicated at 16 for insuring umrorm air distribution to the burner viacircular air register C.

blIULllzlI air register C comprises, more specifically, a plurality ofarcuate vanes 19, each of wmcn are plvotally mounted on an associatedaxle 21 ror cltljLlSlflDlfi opening and closing movements. Moreparticularly, each or the vane sup orting axles A1 are rotataoiyjOufndlfid to opposlte sioes or a circular rrame AA whereby the vanesmay be dUJUdLaU-l) opened or closed in unison concurrently withvariation in nrlng rate, by control means to oe herelnalter described.

Lurcular arr register assembly C is located within the scroll plenum 11111 such manner that the clearance between the circular register and thewalls or the plenum diminishes in the direction or the air now throughthe plenum so as to insure unlrorm distribution or air through theregister vanes and into the burner.

the circular register is also located coaxially with respect to thethroat opening of the combustion chamber, as well as with respect to thegas inyectlon ring and oil spray nozzle of the burner, as will morefully hereinafter appear.

the construction of the air register is preferably such that when thevanes are fully closed or shut each vane lies generally within the planeof circumference of the circular register frame. lt is further notedthat the vanes are constructed and arranged so that when they are closedcontiguous edges of ad acent vanes partially overlap one another inshingle-like arrangement, as shown in Fig. 5, for example. because whenthe vanes are closed to near shut position during operation of theburner within its lowermost firing range, a highly desirable spiralmotion will be imparted to the air now through the register vanes as itpasses into the combustion chamber. The importance and significance ofinducing a spiral action to the air draft during low load operatingconditions will be described more fully hereinafter.

Each of the vane axles 21 may be provided with a pinion or spur gear,such as indicated at 23, adjacent its rearwardly projecting end. Tocontrol opening and closing movements of the vanes 19 in unison a ringgear 24 may be provided in mesh engagement with all of the vane axlepinions 23. Selective movement of ring gear 24 in clockwise orcounter-clockwise direction may be controlled through manipulation ofcontrol lever 26 provided with a spur gear or pinion 27 in meshengagement with ring gear 24. Referring specifically to Fig. 1, it isseen that upward movement of lever 26 will through its spur gearconnection with the ring gear,

cause the latter to move in a clockwise direction for chronizing theopening and closing movements of the circular air register vanesconcurrently with variations 'lhis arrangement is important v in the"air aiidfuelsupplyto the burner, a manual control station, indicatedgenran' at G,"may b'eprovided. More specifically, control station Gcomprises a manual control lever 50, pivoted as at to quadrant 52 andpivotally connected "byjlink arm '53 to mul ti-Iouve'r fair damper 54,which said damper is'in communication with fan housing for regulatingthe volume of 'air flow into the blower'iinit. c sed arm "50 is alsopivotally corinetedtb g'as valve55 by a link arm "56. Control arm 50 isfurther connected to control lever 26 by link "5622. I I

Fromtlieforegoin'g arrangem nt, it is seen that when mastercontrollev'er 50 is moved upwards, the damper blades "57 of -niul'tilo'u ver damper S i will move toward closed position throughconventional linkage comprising a control bar '59 and blade levers 61),thereby restricti'ng the volume "of 'air into blower unit 19. Upwardmovement of 'i'n'aster control lever 50 will also cause corfespondirigclosing of "gas'valve 55 and circular air register C by virtue of linkconnections 56 and 56a with these latter components. a

It is evidentfof course, "that downward movement of manuareontreiieverSD will, through the linkageabove mentioned, cause correspondingsimultaneous opening of theinultidouver damper 54, air register assemblyC, and gas valv'e ss.

It'vvill ber'ea'dily understood, of course, that when oil instead of'gasis burned, other linkage corresponding to that described above foropening and closing the gas valve may be provided'for similarlycontrolling the oil supply to thebiirner upon movement of manual controllever 50 ana'iapmp'e'r relation to the'air supply.

In addition to'providing a manual control station foradjustablyre'g'ulating the supply of fuel and air depend ing on existingload conditions concurrently with adjustmerit of 'v'ane' opening of anadjustable vane register as abov'e' describ'ed, it is desirable in manycommercial installations embodying theinvehtion to provide a suitablesysmm for automatically controlling both the air and fuel supply to theburner according to varying load conditions. It will sufiice to remarkthat various types of automatic or semi automatic control systems havebeen developed and used i'n'the past for controlling air and fuel supplyto a burner according to heat requirement of the boileror other unit inconnection with which the burner is employed for generating heat. Suchautomatic or semi-automatic control systems are, accordingly, well knownin the art, and further elaboration in regard to such'sy'stems'istherefore considered unnecessary, beyond recognizing that by thisinvention such automatic means of varying rate of fuel and air supply toa burner, will concurrently'vary the vanes of an adjustable vane airregister as above described from a closed or nearly closed position atminimum firing rate to a largely open position at maximum firing rate.

The actualburner unit shown in the drawings comprising gas burnerassembly D, oil injection assembly E, and combustion chamber, abovementioned, inayalso be of more or les conventional design. Morespecifically, the entrance to combustion chamber F is truncated conicalshape in cross-section defining a restricted throat 27, and is formed ofsuitable plastic refractory material.

The oil burner assembly E is shown as comprising a mechanical atomizer(or steam atomizer) 28 adapted for connection to a source of oil (andsteam) under pressure (not shown), an oil supply tube 29 and a spraynozzle tip 31. The supply tube 29 andspray tip 31 are housed within'aguide tube 32 which, inturn,'isprovided with an oil burner shield 33adjacent its forward end.

Thegas'burner assembly-D-is shown as comprising a gas ring 3-4 adaptedforconnection via supply conduit 35 to a source of gas under pressure(not shown) and-formed with-a plurality of; gas jets-or openings 36through which gas is supplied tothe combustion chamber.

Generally speaking, whenaburner of the:generaltype above described isoperated within a firing range at or "approaching its maximum firing"rate, no particular "diffi- 'lent intermixing between thefuel and airby virtue of the decreased volume of air and fuel being introduced intothe combustion chamber at the lower firing ranges.

As hereinabove pointed out, the more conventional oil or gas burnersemploying a scroll plenum or a circular or rectangular plenum inconjunction with a fixed vane type register, are incapable of beingoperated within a firing range inuc h below one-fourth to one-fifth ofmaximum capacityi. e. when an attempt is made to operate the burner at afiring rate between one-fifth to'onetenth of maximum capacity, impropercombustion, or failure of combustion, will result, due .principallytolack of sufficieiit rotational air velocity toprovide adequateturbulent intermixing of the fuel and the air.

However, in burners constructed accordingto the present invention whensuch a burner is-operated in-itslower firing range, the air registervanes arepreferably closed to practically fully shut position whereatthe contiguous edges of adjacent arcuate vanes partially overlieor-overlap one another inshingle-like arrangement. Indeed, ex-

cellentresults are obtained in operatingthe burner within itslower-most---firing range by closing theregister vanes to a point wheresubstantially only air leakage through the vanesis permitted. By closingthevanes tothis extent, 'sufficient resistance is built up to overcomethe natural'direction-al-flow of air aroundthe outer surface's of thescrollnplenumto insure uniform distribution 'a'nd flow of air throughthe register vanes. In this connection, it is pointed out that if afixed or set open vane register is employed with a=scroll plenum thefixedvanes'will'not provide sufficient-resistance at low loads or firingrates-to the directional'flow of the 'air around the-plenum t'o'pr'event substantiallyall "of the air flow from entering the burnerthrough a localized area of the register-such as the one vaneopeninglo'cate'd at the point of minimum clearance between the registerand the volute'walls of' tlie plenum. However, and as above stated, byclosing-the adjustable vane register to a point where'only minimum airleakage-ispermitted through the'van'es, s'ufiicie'nt resist-an'ce isbuilt up to overcome the directional flow of the air -and eauseittouniformly enter through a lhinstead of simply one-or several, of thevanes.

A further advantageous and important factor in closing the air-registervanesto a point where' only air leakage is permitted during operation ofthe burner within its lower-most range is that the overlappedarrange'mentof the vanes imparts a highly desirable swirling motion'tothe air'flowing into the "combustion'chamber.

'Moreparticularly, it has been determined from experience that apronounced swirling motion imparted -to the air willpro'duce andmaintain optimum efiiciency between gas and air mix, and it isparticularly desirable, of course, to be'able' to 'inaintai'n optimumefficiency betweenfuel and-air mix when the burner is operating in itslowermost firing range, as well as through its upper firing range.

Although, it'might perhapsbeexpected that reasonably satisfactoryadmixture ofw-gas and -air would be-obtained under theselatteroperatingconditions; it hasbeen found,

very-surprisingly; that substantially equally ood: results are obtainedin oper-at-ing the unit as #anpil "bu'rn'er.

More'particularly,"it has been found tliat the flov'v cfair enteringthrough throat 27 and into the combustion chamber proper will actuallycause the comparatively small conical shaped atomized oil spray injectedfrom nozzle tip 31 to be mushroomed or sucked outwardly toward thetruncated conical shaped walls of the burner resulting in intimateintermixing of the oil spray particles with the air stream to insurecomplete combustion with a minimum of excess air. This mushroomingoutwardly of the oil spray and consequent admixture with the swirlingair fiow will occur even when the amounts of oil and air beingintroduced into the chamber have been reduced to such an extent that theburner is operating at or approaching one-tenth of its maximum firingcapacity.

Although the present invention has been described in some detail by wayof illustration and example for purposes of clarity and understanding,it is understood that certain changes and modification may be practicedwithin the spirit of the invention as limited only by the scope of theclaims appended hereto.

I claim:

1. In a forced air draft oil or gas burner of the type in which airunder pressure is supplied to the combustion chamber for intermixingwith the fuel to be burned, the combination comprising: a blowerassembly for inducing a forced draft of air; adjustable damper meansassociated with said blower assembly for regulating volume of air flowthrough said blower assembly; a scroll plenum in communication with saidblower assembly; a circular air register for imparting a swirling motionto air discharged therefrom disposed interiorly of said scroll plenumcomprising a circular frame; a plurality of vanes pivotally mounted tosaid frame for movement from a closed position, whereat said vanes liegenerally within the line of circumference of said circular frame andwith contiguous edges of adjacent vanes overlapped in shingle-likearrangement, to an open position, whereat said vanes are disposedgenerally radially with respect to said circular frame; said circularair register disposed within said scroll plenum with the clearancebetween the circular register and the volute walls of the scroll plenumdiminishing in the direction of air flow from said blower assemblythrough said plenum; an entrance to a combustion chamber; said circularair register disposed in coaxial alignment with respect to saidentrance; fuel supply means; adjustable regulating means for regulatingthe fuel supply to said entrance; and manual control means associatedwith said damper means, said vanes of said circular air register, andsaid adjustable fuel supply means, for simultaneously regulatingproportionate fuel and air supply to said entrance in relation tovarying load requirements of the burner concurrently with air registervane control.

2. In a forced air draft oil or gas burner of the type in which airunder pressure is supplied to the combustion chamber for intermixingwith the fuel to be burned, the combination comprising: a blowerassembly for supplying substantially of all combustion air; adjustabledamper means operably associated with said blower assembly forregulating volume of air flow through said blower assembly; a windbox incommunication with said blower assembly; a circular air register toimpart a swirl to air discharged therefrom disposed interiorly of saidwindbox comprising a circular frame; a plurality of vanes pivotallymounted to said frame for movement from a closed position to an openposition to impart varying degrees of swirl to air passing through saidregister; an entrance to a combustion chamber; said circular airregister disposed in coaxial alignment with respect to said entrance;fuel supply means located adjacent said entrance; adjustable fuelregulating means for regulating the fuel supply to said entrance; andmanual control means operably associated with said damper means, saidvanes of said circular air register, and said adjustable fuel regulating means, operable to substantially simultaneously relatively open andclose said damper means, said vanes, and said fuel regulating meansproportionate to the increase and decrease respectively of the loadrequirements of the burner.

References Cited in the file of this patent UNITED STATES PATENTS1,684,079 White Sept. 11, 1928 1,738,176 Dyer Dec. 3, 1929 2,203,553Thoresen June 4, 1940 2,211,684 Baker Aug. 13, 1940 2,382,913 RobinsonAug. 14, 1945 2,387,280 Mcllvaine Oct. 13, 1945 2,473,347 Sanborn June14, 1949

